question is though, how do you get an almost 3 yr old to change his diet and not eat what his 2 older siblings do?

All I can say from that, in my situtation where both kids of mine have suspected wheat and milk allergies, make small whole family changes. Not just for 1 child but change the entire family to eatting healthier, in small subtle doses is less noticable Food dyes can deffinately change good behavior to a wacky nutty kid. Start small like cutting back on the food items with dyes and slowly switching over to items that have natural dyes. One small example is regular go-gurts have a ton of dye in them but if you buy the organic ones like say Stoneyfield brand it has color to the yogurt but it is a natural dye like beet juice but it still tastes the same as the go-gurt one.

question is though, how do you get an almost 3 yr old to change his diet and not eat what his 2 older siblings do?

Change everyone's diet, unfortunately. That's what my parents did with me and my sibs when my brother got diabetes. He was 5. He's 24 now and very healthy...so it worked!

Maybe it won't come to that though, if you can find a time-out that will keep him hemmed in. We don't have any empty corners here so I put DD in the laundry room (with the light on and without the bin of clothespins that she loves to play with). It's the only room without toys! LOL She's very social and very attached so the closed door is very effective. She still sometimes hits though.

I am beginning to think that is more of an attention thing/ being tired thing. Today he napped in the car in the afternoon, and he's been soooooo much better behaved. Ive also started babysitting for a 3 mo old so its very hard for him to have my 100% attention for the passed 3 weeks. I do sit for a 3 yr old too, but I've had him for 2 yrs so he and my son play together.

I do still plan on eliminating as much 'junk' as I can though, which will require a trip to the Whole Foods as we don't have many 'natural' things in my normal grocery store.